Lecture 5 Flashcards
How do plants perceive and respond to light stimuli? Plants have several receptor pigments that perceive light and control behavior and development. They do this partly by regulating gene expression.
true or false; plants can “see” light
true
What does plants seeing light affect
germination seedling development phototropism photosynthesis shade avoidance flowering circadian rythmns photmorphogenesis
What does it mean by photomorphogenesis
creation of form in the light
define nutation
circular swaying movement of the tip of growing shoot
true or false; light induces morphological changes in seedlings
true
What do you call the creation of form, of seedlings grown in the dark
skotomorphogenesis or etiolation
describe the characteristics of the seedlings grown in the dark
tall leaves are yellow green chloroplasts are not properly developed little chlorphyll leaves are not fully expanded or open
What do you call the creation of form in the light
photomorphogenesis
What happens eg. in potatoes when the growing conditions of plants are shifted from dark to light
plants undergo de-etiolation
- sprouting potatoes in the dark
- shoots greening up in the light
Why is harmful to eat green potatoes
solanine is present in the green areas
- can occur in improperly stored potatoes
- solanine is harmful when ingested and can be toxic in large quantities
true or false; environment has the a large effect on the expression of a plants’ genes
true
define germination
beginning of growth by seed
define photosynthesis
conversion of light energy to chemical energy
true or false; wavelengths and the light intensity that plants perceive have a great impact on their growth
true
What wavelength affects photosynthesis
400-700nm is photosynthetically active radiation
What does it mean by phototropism
growth towards the light
What wavelength and light color affects phototropism
- blue light causes plant to bend towards the light
- multiple photoreceptors are involved in detecting the blue light
- experiment called: determining the action spectrum (allows us to determine the wavelength perceived by a plant)
what light causes plants to grow out of the shade and into the light
far red light
what light do green leaves absorb
red light
- increases the proportion of far red light relative to red light
- this is detected by the plants and they grow to taller to out compete other plants
What are the light receptors in humans
humans have 4 light receptor pigments
- 3 for each of the primary colors in our cone cells in the retina
- 1 in our rod cells
true or false; plants also have many photoreceptors for blue and red light
true
What are phototropins
detect blue light
what are phytochromes
detect red light
What are cryptochromes
detect blue light
Describe the structure of phytochromes
- is a dimer
- 2 identical proteins that are dimerized together to become one big molecule
- each protein has a domain ( 2 domains in total); for photoreceptor activity and kinase activity
- each molecule is attached to a chromophore
- activated by light
What is a chromophore
detects light
organic molecule
true or false; there are two forms of phytochrome that absorb different wavelengths
true
What are the two forms of phytochrome
Pr (660 nm)
Pfr (730nm)
What does Pr absorb
red light
what does Pfr absorb
far red light (longer wavelength)
true or false; phytochrome is a molecular switching mechanism
true
true or false; Pfr is the biologically active form of phytochrome
true
what reverses phytochrome
light
What happens in the dark to Pfr
slowly reverses to Pr
- slowly degraded and made
what are the applications of studying light regulation of plant development
designing
selecting crops that can cope with being crowded
true or false; most leaves are specialized for light absorption
true
- like a solar panel, leaves are often broad and flat to optimize light harvesting
how come modern maize plants can be planted at high density; increasing their yield per hectare
Plants selected by plant breeders have upright leaves to help capture sunlight energy under crowded conditions.
They can be machine planted at high density (up to 100 000 plants per hectare)
What is the effect of red light
increased germination
inhibit stem elongation and lateral root formation
stimulates leaf expansion, cholorplast development, red flower coloration, spore germination
What is the effect of far red light
inhibits germination
what is the photoreceptor responsible for perceiving red and far red light
phytochrome
What does the kinase domain trigger
triggers kinase cascade
of downstream events
What are phototropism involved in
phototropism
what is the survival advantage of etiolation
increases the plants’ chances of reaching light before their stored energy supplies are exhausted
